Seminar: D-Brane Model Building Tools Beyond Factorisable Tori

Geometric constructions of D-brane models provide powerful tools to obtain Type II string vacua with particle physics spectra. Deriving the corresponding low-energy effective action, such as gauge couplings at one-loop and Yukawa interactions already at tree-level, usually require to go well beyond supergravity, in particular using CFT techniques. This kind of D-brane model building has in the past mainly focused on toroidal orbifolds, where the underlying six-torus factorises into three two-tori. However, other factorisations are interesting due to (i) their reduced number of twisted geometric moduli and (ii) their potential to accommodate higher-form background fluxes. In this talk, I will first discuss generic model building requirements and then proceed with exemplary so-called non-factorisable Z4 orientifolds, first in terms of the topology of three-cycles and secondly by means of a factorised description with an additional shift symmetry acting on various two-tori simultaneously. This latter description allows for adjustments of standard CFT techniques, by which the non-chiral spectrum and the low-energy effective action can be derived.